Fix --compile_all flag (--compile-all is wrong)

runtime/observatory/tests/service/get_vm_rpc_test.dart

 // Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
-// VMOptions=--compile-all --error_on_bad_type --error_on_bad_override
+// VMOptions=--compile_all --error_on_bad_type --error_on_bad_override
 
 import 'package:observatory/service_io.dart';
 import 'package:unittest/unittest.dart';
 
 import 'test_helper.dart';
 
 var tests = [
   (VM vm) async {
     var result = await vm.invokeRpcNoUpgrade('getVM', {});
     expect(result['type'], equals('VM'));
     expect(result['architectureBits'], isPositive);
     expect(result['targetCPU'], new isInstanceOf<String>());
     expect(result['hostCPU'], new isInstanceOf<String>());
     expect(result['version'], new isInstanceOf<String>());
     expect(result['pid'], new isInstanceOf<String>());
     expect(result['startTime'], isPositive);
     expect(result['isolates'].length, isPositive);
     expect(result['isolates'][0]['type'], equals('@Isolate'));
     expect(result['_assertsEnabled'], new isInstanceOf<bool>());
     expect(result['_typeChecksEnabled'], new isInstanceOf<bool>());
   },
 ];
 
 main(args) async => runVMTests(args, tests);